The present invention relates to a multi-joint arm type measurement apparatus. Particularly, the present invention relates to improvements on a multi joint arm type measurement apparatus having a plurality of probes (for example, a contact probe and a non-contact probe) mounted at a tip of a multi-joint mechanism and configured to appropriately use the probes depending on an area to be measured.
As exemplified in FIG. 1A, a multi joint arm type measurement apparatus having a multi-joint mechanism 10 has been known (Patent Documents 1 and 2). Here, the multi-joint mechanism 10 includes a base 12 fixed to a working table or tripod (not shown), a first arm. 16 supported to the base 12 via a first joint 14, a second arm 20 supported to a tip of the first arm 16 via a second joint 18, an arm head 24 supported to a tip of the second arm 20 via a third joint 22, a grip 26 for enabling an operator to hold the arm head 24, a contact probe (also referred to as a hard probe) 30 such as a ball probe fixed to a tip of the arm head 24, and a rotation mechanism of seven axes shown in FIG. 1.
As specifically shown in FIG. 1B, an optical probe for performing extensive non-contact measurement in conformity to an area to be measured is attached to the arm head 24 via a laser attachment bracket 32. For example, the optical probe is a laser probe 34 in which reflected light of laser light, which is emitted from a laser illumination port 34A, is captured at an incident port 34B to obtain a sectional shape of the area to be measured by a light-section method.
In this way, the two probes 30, 34 are provided, so that it is possible to perform hybrid measurement of the high-precision contact measurement and the extensive non-contact measurement.    [Patent Document 1] Japanese Patent Application Publication No. 2005-517914A    [Patent Document 2] Japanese Patent Application Publication No. 2007-527323A
When fixing the laser probe 34 to the arm head 24, balls 32A provided at three portions of the back side of the laser attachment bracket 32, as shown in FIG. 2A, and rollers 25A provided at three portions of an attachment base 25 fixed to the arm head 24, as shown in FIG. 2B, are matched with each other and a laser probe fastening ring 36 is fastened (screw fastened) thereto, so that the laser attachment bracket 32 is fixed to the arm head 24.
However, when the fixing is made by the screw fastening, a relatively position is uniquely determined. Therefore, the laser probe 34 and a workpiece position overlap with each other, so that a workpiece may not be seen well. Also, when illuminating the laser in a lateral direction, it is necessary to perform the measurement with the grip 26 being positioned laterally. At this state, however, when the measurement is performed at a high position, the arm should be raised high. As a result, it is difficult to perform the measurement for a long time.
In the meantime, Patent Documents 1 and 2 disclose that the optical probe is configured to be relatively rotatable around the contact probe. However, since a relative rotation position is free and is not restrained, there is a concern that the rotation will be made during the measurement. As a result, it is not possible to perform the high-precision measurement.